Developmental studies on intraruminal devices for ruminants

Simpson, Anna Marie (1985) Developmental studies on intraruminal devices for ruminants. PhD thesis, University of Glasgow.

Abstract

This thesis deals with the development and application of a slow release intraruminal bolus for administration to cattle and sheep. In the first instance the bolus was formulated as a short term cattle trace mineral supplement which contained copper, cobalt, manganese, zinc, selenium and iodine in the form of readily available salts in proportions which fulfilled the ARC (1965) mineral requirements of cattle for 30 days. In early prototypes the salts were compressed at high pressure with 0.7 mm iron filings in 50-50 proportions by a commercial tabletting firm to produce a lozenge shaped tablet which had a density of ≥3.0 gcm -3 , sufficient to lodge in the reticulum of cattle and be retrievable from this site in fistulated cows. Further development work followed, with the acquisition of a bench press capable of compacting cylindrically shaped boluses of varying length and diameter in the laboratory. Copper oxide needles of 2-4 mm were chosen to replace iron filings in laboratory models. It was found that boluses eroded over a period of weeks partly by abrasion with another bolus and partly through dissolution of ingredients and that the pattern of erosion could be altered by changing certain features of the boluses such as coating type, surface area initially exposed, and mineral salts constituents such as zinc oxide and zinc sulphate heptahydrate. The stage was reached when a reasonably predictable pattern of erosion took place over 4-6 weeks in fistulated cows with one particular bolus formulation. Field trials were carried out using a treatment of two boluses in fattening lambs and in a herd of beef suckler calves. While treated lambs showed enhanced blood and liver copper levels compared to control lambs, only 50% of the boluses were recovered after twenty-seven days and it was speculated that the remaining 50% had been regurgitated and possibly chewed. In the beef suckler calves' trial, improved blood copper levels were found in the treated group. An attempt was then made to produce the cylindrical mineral bolus of the same dimensions as that produced in the laboratory on a commercial factory scale. Various formulae were attempted to be produced in two sizes of cylindrical bolus, a 16 mm diameter and 25 mm diameter size. However it was found that although it was possible to produce these formulae at speed on a large scale, the length of the boluses was about half that of those produced in the laboratory, and was restricted by the physical dimensions of the Bipel press on which the boluses were produced. It was not possible to find a commercial press in Britain capable of producing a compacted bolus of the length required. The 16 mm diameter boluses containing copper oxide needles were experimentally administered to lambs and ewes, and were found to significantly increase the liver copper levels although again there was some failure to recover boluses in the group of lambs (57% were found after twenty-four days) which was thought to be related to the density of the bolus. Further development of the bolus was continued in the laboratory, and the medicated ingredients, monensin sodium, levamisole hydrochloride, morantel tartrate and citrate and ivermectin were experimentally included in the formulation. Of these, monensin, levamisole and ivermectin boluses produced reasonably promising results, and ivermectin boluses were chosen for further development. In a controlled experimental challenge, boluses containing ivermectin were found to be >99% effective against Ostertagia ostertagi and Cooperia oncophora in housed calves. In an outdoor trial of the same bolus type over the grazing season, parasitism was apparently completely controlled in calves for a period of eight weeks which coincided with the active life of the bolus. Thereafter there was a gradual increase in faecal egg counts followed by a later increase at around four months in plasma pepsinogen levels. At necropsy the bolused group had a reduced parasite burden compared to the control group although this was not statistically significant. This trial was followed by a period of further commercial involvement during which it was attempted, with limited success, to produce a bolus containing ivermectin on a large scale. During this period many of the basic design features of the bolus were altered in an attempt to suit existing commercial machinery and processes.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Animal sciences
• Date of Award: 1985
• Depositing User: Enlighten Team
• Unique ID: glathesis:1985-76556
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 19 Nov 2019 14:09
• Last Modified: 19 Nov 2019 14:09
• URI: https://theses.gla.ac.uk/id/eprint/76556